( informal ) used to say that you are not stupid enough to believe what sb is telling you :
Oh yeah? I wasn't born yesterday, you know.
( informal ) used to say that you are not stupid enough to believe what sb is telling you :
Oh yeah? I wasn't born yesterday, you know.
Oxford Advanced Learner's English Dictionary. Оксфордский английский словарь для изучающик язык на продвинутом уровне. 2005